1. Field of The Invention
The field of the present invention relates generally to an apparatus and processes which employ pollution abatement techniques to treat a gas containing metal halides or organo substituted metal halides and recover the metal in a reusable form. In a specific application, excess coating materials generated by a coating apparatus utilized in glass manufacture are treated.
2. Description of the Prior Art
Glass surfaces are found in a multitude of objects, including glass containers and bottles. However, when freshly formed glass surfaces are moved over one another at the slightest contact pressure, visible abrasions will be formed. Since it has long been recognized that abrasions reduce the potential strength of a glass container, and glass containers are handled in filling lines at very high rates in conditions where the glass containers will often come into contact with each other, glass manufacturers have sought means to protect glass surfaces.
It has been found that glass may advantageously be coated utilizing hot-end coating operations between a glass forming machine and a lehr in which the formed glass is annealed. In such a process, a metal oxide coating is formed on the hot glass surface. In particular, it has been found that metal oxide coatings are useful in preventing abrasions.
Metal oxide coatings may be formed during hot-end coating operations by treating hot glass surfaces with metal halides or organo substituted metal halides. Thus, by way of example only, stannic chloride vapor has been utilized in such operations, as is more fully described in U.S. Pat. No. 3,561,940, the disclosure of which is specifically incorporated herein by reference. Another example of a metal halide now in commercial use is titanium tetrachloride. Suitable examples of organo substituted metallic halides include tin halides, such as diisopropyl tin dibromide, trimethyl tin chloride, tripropyl tin chloride and other compounds noted in U.S. Pat. No. 3,956,532, the disclosure of which is specifically incorporated herein by reference. However, conventional coating operations require an excess or overspray of the coating material in order to achieve a desired coating thickness. The amount of overspray will not only affect the cost of the materials needed to coat a given quantity of glass objects, but it will also contribute to the amount of coating materials which are introduced into the environment surrounding the coating apparatus.
It is suspected that metal halides and organo substituted metal halides pose a health hazard to industrial workers who are continually exposed to relatively low levels of these materials over a long period of time. Metallic halide compounds and organo substituted metallic halide compounds will decompose to form a strong acid or a hydrogen halide gas as well as a metallic oxide upon contact with sufficient moisture or heat. Thus, metallic halides and organo substituted metallic halides pose health risks not only due to their metallic content, but also due to their corrosive properties. Additionally, the same corrosive properties which pose health hazards will also lead to property damage and environmental concerns if the metallic halides and organo substituted metallic halides are not removed from waste gases.
Despite the above-noted problems, conventional apparatus and methods of coating have taken few preventive measures to reduce the amount of overspray which is discharged outside of the coating apparatus. As an example, previous methods of coating have often relied upon elevated exhaust ducts to reduce the concentration of excess coating vapors released to the environment. Such exhaust ducts create an elevated plume which is eventually distributed over a large area. While such devices decrease the concentration of metallic coating materials which are found in a small unit of surrounding air, such as a cubic meter, the metallic coating materials are still emitted to the environment. Thus, there exists a need for an effective means for removing metal halides and organo substituted metal halides from the environment when such compounds are discharged in a waste gas from any industrial application, one example of which is hot-end metallic glass coating operations.